Apparatus for controlling a plurality of injection molding machines

ABSTRACT

An apparatus for controlling a plurality of injection molding machines is disclosed wherein each injection molding machine is provided with a digital memory. The memories are provided with data from a central unit and are activated as a function of travel of appropriate machine parts of the respective molding machines.

States Patent 1191 [111 3,760,251

Posl et al. 1- Sept. 18, 1973 APPARATUS FOR CONTROLLING A {56].References Cited IPLIURALITY OF INJECTION MOLDING UNITED STATES PATENTSMACHINES 3,465,298 9/1969 Duke et al. 3l8/57l x [75] Inventors: RudolfPosl; Burkard Popp, both of r a e Nuremberg Germany 3,626,385 12 1971Bouman 318/562 x [73] Assignee: Siemens Aktiengesellschaft', Munich,3,372.568 3/1968 Lemelson 318/562 X Germany Primary Examiner-B. Dobeck[22] Flled. June 12, 1972 Atmmey Hugh A Chapin [2]] Appl. No.: 261,658 1[57] ABSTRACT [30] Foreign Application p i i Data An apparatus forcontrolling a plurality of injection June 1971 German P 21 29 419 9molding machines is disclosed wherein each injection y molding machineis provided with a digital memory. [52] U S Cl 318/601 318/562 235/15111 The memories are provided with data from a central ['51] Gosh B unitand are activated as a function of travel of appro- [58]. Field 608 57priate machine parts of the respective molding ma 318/601; 340/1725;235/l51.ll

chines.

6 Claims, 2 Drawing Figures E OUTPUT STORAGE 'FRUMB j DEVICE DlSTRIBUTDR MEMORY [COUNTER o I 51 fl-- 51 A Q 53 i 55 GATE CIDMPARATDRBLOCK i as j COUPLER FRnMA p APPARATUS FOR CONTROLLING A PLURALITY OFINJECTION MOLDING MACHINES BACKGROUND OF THE INVENTION The inventionrelates to an apparatus for controlling a plurality of injection moldingmachines such as those for molding plastic. More particularly, theinvention relates to such an apparatus having a central unit forproviding data to a plurality of digital memories, each memory beingassociated with its respective molding machine.

When automating an injection molding machine,

once the operating parameters or measured values have been empiricallydetermined, it is a special problem to have these parameters or valuesavailable at any time in a reproducible manner for the control of themachine. Such parameters and operating values include machine travel atwhich some operating command is to be transmitted, or times, pressuresand temperatures.

A solution to this problem has already been suggested for an injectionmolding machine equipped with a device for storing measured values andoperational quantities wherein the operational quantities are insertedthrough a logic circuit into storage locations of a digital memory andrecalled from this memory by commands such as definite position valuesderived from the machine for controlling the same. The digital memory isbuilt up with integrated circuits and the operational quantities aretemperature, pressure or measured values, especially travel signals independence upon the position of a functional-mode selection switch. Inconnection with this solution, reference may be had to Swiss Pat. No.486,940.

The current trend of automation requires that several injection moldingmachines be combined and simultaneously controlled from a centrallocation. This poses the limiting condition on the one hand, that thecentral unit should not be overloaded with tasks with the consequencethat it is necessary to resort to a costly, large process computerhaving a large cycle time, and on the other hand, it is desirable thatthe control unit connected to each machine be relatively simple butnevertheless flexible.

SUMMARY OF THE INVENTION It is an object of the invention to provide anapparatus for controlling a plurality of injection molding machineswhich substantially fulfills the above-stated re.- quirements.Subsidiary to this object, it is an object of the invention to providesuch an apparatus wherein a multiplicity of commands are transmitted ina relatively simple manner to each of the injection molding machines atthe required time.

According to a feature of the invention, a plurality of injectionmolding machines areeach provided with a freely programmable digitalstorage memory which is in turn connected with a central unit from whichcommands can be transferred to the memory. Eachcommand is assigned aposition address corresponding to a desired position of a machine partof the corresponding machine. Each machine has digital positioningdevices for the machine parts to be positioned. Each memory is connectedwith a comparison unit to which also the respective position measuringdevices are connected. All position addresses of each memory can becontinuously and successively compared with the actual position valuefed to'the comparison unit, and in the event of coincidence, thecorresponding stored command can be called up from the memory forcontrolling the respective machine.

In this manner, a relatively simple and flexible control for a pluralityof machines can be achieved, by means of which any desired, freelyselectable number of commands can be called up, for example, at adesired position location of a machine part.

A particularly simple interrogation of the position addresses in thestorage memory is obtained if their sequence in time is controlled by acommand counter which is connected to a timing unit because, for thiscondition, transmission of the stored commands is possible via adistributor which is controlled by this command counter. Since severalposition measuring devices can be associated with each memory, it isfurther advantageous to make the subdivision of the position addressesin time so that, according to a given count of the command counter, onlyone predetermined position measuring system is connected to thecomparison unit.

The above-mentioned digital memory can be designed advantageously fromintegrated circuits, because a relatively simple, space-saving andinexpensive storage of the required data is obtained thereby; however,in lieu of such a storage system, it is also possible to build a memorywith shift registers or magnetic cores.

The apparatus according to the invention is advantageous if the flow ofinformation goes not only from the central unit via the memory to theindividual machines, but also if the position values obtained in settingup the machine, at which any switching actions or commands are to beexecuted, can be fed back from the position measuring device via thememory to the central unit. At the central unit, these commands are thenstored in a suitable manner, for example, on punch cards or perforatedtape. The central unit can comprise, for example, a perforated-tapereader which reads the required program and transmits it to theindividual storage devices. Alternatively, the central unit is part of alarger computer which takes care of higher-order disposition problems.

Although the invention is illustrated and described herein as anapparatus for controlling a plurality of injection molding machines, itis nevertheless not. in tended to be limited to the details shown, sincevarious modifications may be made therein within the scope and the rangeof the claims. The invention, however, together with additional objectsand advantages will be best understood from the following descriptionand in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a block diagram showing thedisposition of the central unitand evaluation devices of the machinecontrol apparatus according to the invention.

FIG. 2 is a detail block diagram showing the components of an evaluationdevice.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, each ofthe injection molding machines 1 is provided with an evaluation device 5which in turn is connected to a central unit 6. Appropriate commands aretransmitted from the central unit 6 to the evaluation device whichcomprises storage and control units. These commands can be additionallyaltered manually by means of decade switched 7.

Each injection molding machine 1 is provided with digital positionmeasuring devices for the machine parts to be controlled. The actualposition values are taken from the respective measuring devices and fedvia line 8 to the evaluation device 5 for the issuance of commands independence upon the position values.

In the illustrated embodiment, three position measuring devices 4 areshown for respectively measuring the position of the injection slide 2,the assembly 3 and the mold-closing part 3a of the injection moldingmachine 1. Each of the measuring devices 4 consists of a magneticdigital absolute scale 40 and a fixed contactless, switchless pickupunit 4b. The pickup unit 4b can be a Hall generator for example. Theindividual position measuring systems 4 are arranged here in each caseparallel to the direction of displacement of the appropriate machinepart.

The evaluation device 5 contains a digital memory 51 made up ofintegrated circuits. Commands from the central unit 6 in the form of thedistances to be travelled and other operational data, such astemperature and pressure can be read into the memory 51. To each of thecommands is assigned a position address which agrees with some actualposition value which can be ascertained by the position measuringdevices 4.

A clock 53 continuously triggers a command counter 52 and, in dependenceupon the position of the counter, one of the position addresses in thememory 51 is always fed to the comparator 57. The position valuesdetermined by the position measuring system 4 are in each instancesupplied to the comparator 57 through coupling means in the form of ameasuring system coupler 58. If the actual position value just measuredagrees with the storage address fed in at the time, the gate 54 isopened and the corresponding command in the memory 51 is fed via thecommand distributor 55, to the corresponding command stage in the outputstorage device 56 and transmitted to the machine control. Thedistributor 55 is also advanced synchronously by the counter 52.

Since there are severalposition measuring devices 4 that provide severalactual values of position simultaneously, the measuring system coupler58 selectively connects the position measuring devices to the comparator57 at respective intervals consisting of a predetermined number ofcycles. The coupler 58 is also controlled by the counter 52.

The organization of the position addresses in the memory 51 is arrangedhere so that, for example, with i 64 possible addresses, forty addressesare assigned to the first measuring system, twenty addresses to thesecond measuring system and four addresses to the third measuringsystem; this ensures that the measuring system coupler 58 is switchedover at the respective corresponding counter positions. The specialfeature of the storage device is that the individual position addressesof the memory 51 are continuously and successively scanned to determinewhether one of these addresses corresponds to any one of the actualposition values just delivered. Thus, far greater flexibility andvariation of control possibilities are obtained than with controlarrangements known up to the present time.

Digital absolute scales are well known (see Control Engineering Nov.1956, page 107-1 13). The code may be represented by openings (opticalsystem) or by magnetic signs as it is here.

What is claimed is:

1. Apparatus for controlling a plurality of injection molding machinessuch as those used for molding plastic, each of the machines havingmovable parts which move in response to predetermined commands, saidapparatus comprising: a central unit for storing and issuing commandsfor operating the respective machines; and a plurality of evaluationdevices respectively connected to said central unit and corresponding torespective ones of the molding machines, each one of said evaluationdevices comprising a programmable digital memory connected to saidcentral unit for receiving commands therefrom for operating the machinecorresponding to said one device, each one of said last-mentionedcommands including a position address corresponding to a positionquantity for a movable part of the machine; digital position measuringdevices mounted relative to the movable parts respectively of themachine for providing actual values of the respective positions of theparts; a comparator; and coupling means connected to said positionmeasuring devices for selectively supplying actual position values tosaid comparator, said comparator being connected to said digital memoryfor continuously comparing all of said position addresses of said memorysequentially with the actual position value supplied by said couplingmeans at a given time and for providing a signal for releasing anappropriate command from said digital memory for controlling the machinecorresponding to said one evaluation device when a position address iscoincident with said last-mentioned actual position value.

2. The apparatus of claim 1 wherein said evaluation device comprises acommand counter connected to said digital memory for controlling thetime sequence of said position addresses for making the comparison insaid comparator, and a clock connected to said command counter forcontinuously triggering the same.

3. The apparatus of claim 2 wherein said evaluation device comprises acommand distributor for receiving and transmitting said command issuedin response to said signal, said command counter being connected to saidcommand distributor for synchronously controlling the same.

4. The apparatus of claim 2 wherein said command counter is connected tosaid coupling means for connecting said position measuring devicesindividually to said comparator in dependence upon the position of saidcounter.

5. The apparatus of claim 1, said memory consisting of integratedcircuits.

6. The apparatus of claim 1, each of said position measuring devicescomprising a digital, absolute, magnetic code scale.

t i i i

1. Apparatus for controlling a plurality of injection molding machinessuch as those used for molding plastic, each of the machines havingmovable parts which move in response to predetermined commands, saidapparatus comprising: a central unit for storing and issuing commandsfor operating the respective machines; and a plurality of evaluationdevices respectively connected to said central unit and corresponding torespective ones of the molding machines, each one of said evaluationdevices comprising a programmable digital memory connected to saidcentral unit for receiving commands therefrom for operating the machinecorresponding to said one device, each one of said lastmentionedcommands including a position address corresponding to a positionquantity for a movable part of the machine; digital position measuringdevices mounted relative to the movable parts respectively of themachine for providing actual values of the respective positions of theparts; a comparator; and coupling means connected to said positionmeasuring devices for selectively supplyIng actual position values tosaid comparator, said comparator being connected to said digital memoryfor continuously comparing all of said position addresses of said memorysequentially with the actual position value supplied by said couplingmeans at a given time and for providing a signal for releasing anappropriate command from said digital memory for controlling the machinecorresponding to said one evaluation device when a position address iscoincident with said lastmentioned actual position value.
 2. Theapparatus of claim 1 wherein said evaluation device comprises a commandcounter connected to said digital memory for controlling the timesequence of said position addresses for making the comparison in saidcomparator, and a clock connected to said command counter forcontinuously triggering the same.
 3. The apparatus of claim 2 whereinsaid evaluation device comprises a command distributor for receiving andtransmitting said command issued in response to said signal, saidcommand counter being connected to said command distributor forsynchronously controlling the same.
 4. The apparatus of claim 2 whereinsaid command counter is connected to said coupling means for connectingsaid position measuring devices individually to said comparator independence upon the position of said counter.
 5. The apparatus of claim1, said memory consisting of integrated circuits.
 6. The apparatus ofclaim 1, each of said position measuring devices comprising a digital,absolute, magnetic code scale.